Fix linter errors for RubyMine and some YARD

What does this MR do and why?

For the Workspaces bounded context:

• Adds suppression for false-positive RubyMine linter errors (these have been reported to JetBrains)
• Fixes some legitimate RubyMine linter errors
• Fixes some (but not all) missing YARD annotations

References

• https://handbook.gitlab.com/handbook/tools-and-tips/editors-and-ides/jetbrains-ides/code-inspection/why-are-there-noinspection-comments/

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

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How to set up and validate locally

• See https://handbook.gitlab.com/handbook/tools-and-tips/editors-and-ides/jetbrains-ides/code-inspection/#code-inspections